RUDDER TRIALS. U. S. S. STERETT. 311 



EFFECT OF WAVES. 



The turning trials on June 8 were run in a choppy sea with breaking 

 waves of height about four feet. The wind was estimated at "four" of 

 Beaufort's scale. 



Turns were made at speeds from 15 to 23 knots. When turning at 

 23 knots, water came over the deck in such quantities that the electrical 

 leads from the recording gear were short-circuited. The trials were therefore 

 discontinued. 



The results obtained this day were irregular and chiefly of interest when 

 compared with the data from smooth- water turns. The maximum recorded 

 moment on any turn was 35 per cent greater than the maximum moment 

 recorded the following day for the same speed and helm. The effect of 

 waves was to cause the force curve to fluctuate by a total amount equal 

 to 40 per cent of the average ordinate. The average moment on steady 

 turning was 15 per cent greater than the corresponding moment in smooth 

 water. 



CONCLUSIONS. 



The material presented above seems to warrant the following 

 conclusions : — 



1 . A given coeflficient of reduction for Joessel's formula may be applied 



to similar ships, with rudders of the same type, only for the same helm-angle 



V 

 and at corresponding speeds, i. e.,—/y= = constant. 



2. In turning with the helm alone, the maximum tension in the rudder 

 chain (including friction of gear) occurs at the instant the helm has reached 

 its extreme position, and amounts to 139 per cent of the tension when the 

 ship is turning uniformly, at 28 knots and 35° helm. 



3. The maximum twisting moment on the rudder post occurs at the 

 same instant as (2) above, and amounts to 130 per cent of the moment when 

 ship is turning uniformly at 28 knots and 35° helm. 



4. The rudder moment to "meet ship," when turning amounts to about 

 112 per cent of the moment, exerted in steady turning with same speed 

 and helm. 



5. The effect of waves of height about four feet is to produce a maximum 

 moment, when turning, of 135 per cent of the maximum moment when turn- 

 ing in quiet water. 



6. The force exerted by the steering engine to overcome the friction 

 of the leads to the rudder yoke is 24 per cent of the maximum force exerted 



